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Date: Tue, 24 May 2022 13:33:37 +0200 From: Alexander Lobakin <alexandr.lobakin@...el.com> To: Masahiro Yamada <masahiroy@...nel.org> Cc: Alexander Lobakin <alexandr.lobakin@...el.com>, linux-hardening@...r.kernel.org, X86 ML <x86@...nel.org>, Borislav Petkov <bp@...en8.de>, Jesse Brandeburg <jesse.brandeburg@...el.com>, Kristen Carlson Accardi <kristen@...ux.intel.com>, Kees Cook <keescook@...omium.org>, Miklos Szeredi <miklos@...redi.hu>, Ard Biesheuvel <ardb@...nel.org>, Tony Luck <tony.luck@...el.com>, Bruce Schlobohm <bruce.schlobohm@...el.com>, Jessica Yu <jeyu@...nel.org>, kernel test robot <lkp@...el.com>, Miroslav Benes <mbenes@...e.cz>, Evgenii Shatokhin <eshatokhin@...tuozzo.com>, Jonathan Corbet <corbet@....net>, Michal Marek <michal.lkml@...kovi.net>, Nick Desaulniers <ndesaulniers@...gle.com>, Herbert Xu <herbert@...dor.apana.org.au>, "David S. Miller" <davem@...emloft.net>, Thomas Gleixner <tglx@...utronix.de>, Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...hat.com>, Christoph Hellwig <hch@....de>, Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Arnd Bergmann <arnd@...db.de>, Josh Poimboeuf <jpoimboe@...hat.com>, Nathan Chancellor <nathan@...nel.org>, Masami Hiramatsu <mhiramat@...nel.org>, Marios Pomonis <pomonis@...gle.com>, Sami Tolvanen <samitolvanen@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>, Nicolas Pitre <nico@...xnic.net>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>, linux-arch <linux-arch@...r.kernel.org>, live-patching@...r.kernel.org, clang-built-linux <llvm@...ts.linux.dev> Subject: Re: [PATCH v10 01/15] modpost: fix removing numeric suffixes From: Masahiro Yamada <masahiroy@...nel.org> Date: Tue, 24 May 2022 03:04:00 +0900 > On Thu, Feb 10, 2022 at 3:59 AM Alexander Lobakin > <alexandr.lobakin@...el.com> wrote: > > > > `-z unique-symbol` linker flag which is planned to use with FG-KASLR > > to simplify livepatching (hopefully globally later on) triggers the > > following: > > > > ERROR: modpost: "param_set_uint.0" [vmlinux] is a static EXPORT_SYMBOL > > > > The reason is that for now the condition from remove_dot(): > > > > if (m && (s[n + m] == '.' || s[n + m] == 0)) > > > > which was designed to test if it's a dot or a '\0' after the suffix > > is never satisfied. > > This is due to that `s[n + m]` always points to the last digit of a > > numeric suffix, not on the symbol next to it (from a custom debug > > print added to modpost): > > > > param_set_uint.0, s[n + m] is '0', s[n + m + 1] is '\0' > > > > So it's off-by-one and was like that since 2014. > > Fix this for the sake of upcoming features, but don't bother > > stable-backporting, as it's well hidden -- apart from that LD flag, > > can be triggered only by GCC LTO which never landed upstream. > > > > Fixes: fcd38ed0ff26 ("scripts: modpost: fix compilation warning") > > Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com> > > --- > > scripts/mod/modpost.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > > index 6bfa33217914..4648b7afe5cc 100644 > > --- a/scripts/mod/modpost.c > > +++ b/scripts/mod/modpost.c > > @@ -1986,7 +1986,7 @@ static char *remove_dot(char *s) > > > > if (n && s[n]) { > > size_t m = strspn(s + n + 1, "0123456789"); > > - if (m && (s[n + m] == '.' || s[n + m] == 0)) > > + if (m && (s[n + m + 1] == '.' || s[n + m + 1] == 0)) > > s[n] = 0; > > > > /* strip trailing .lto */ > > -- > > 2.34.1 > > > > This trivial patch has not been picked up yet. > > I can apply this to my tree, if you want. It's a good idea, I'd like to! I don't use `-z unique-symbol` for FG-KALSR anymore*, but this fix is not directly related to it and can be taken independently. Should I change the commit message or it's ok to take it as it is? > > Please let me know your thoughts. > > > -- > Best Regards > Masahiro Yamada * I'm planning to submit a new rev of FG-KASLR series soon, but since I'm too busy with XDP for now, it will happen no sooner than in a couple months =\ Thanks! Al
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